Starting mechanism for an internal combustion engine



March 1 4, 1961 R. B. RUSSELL.

STARTING MECHANISM FOR AN INTERNAL COMBUSTION ENGINE Filed Oct. 23, 1958m m m m United States Patent i STARTING MECHANISM FOR AN INTERNALCOMBUSTION ENGINE Robert B. Russell, 248 Park St., Newton, Mass.

Filed Oct. 23, 1958, Ser. No. 769,209

1 Claim. (Cl. 123--179) This invention relates to turning devices forimparting a rapidly accelerating movement to a rotatable body, and moreparticularly to manually operated spring starters.

Previous developments in the area of manually operated spring startershave been directed generally toward developing inexpensive starters ofsimple construction for N Patented Mar. 14, 1961 g with various othertypes of motors and I have simply seuse in conjunction with the smallinternal combustion engines on lawnmowers and outboard boat motors. Thestarters hitherto developed, however, have employed a drive mechanism inwhich the initial torque of the spring had to be suflicient in and ofitself to start the drive shaft moving at a rapid rate despitecompression and cold hearing resistances. This has necessitated largeand strong springs which are expensive and hard to wind up.

Therefore it is an object of my invention to provide a manually operatedspring starter for use on small internal combustion engines which gainskinetic energy before engaging the drive shaft of the motor, whichkinetic energy is utilized to counteract the viscosity bonds andstiffness in the bearings, as well as the compression resistance andinertia of the cold motor.

It is a feature of my invention that the coiled spring in my starterengages the drive shaft of a motor by means of drive clutch mechanismwhich includes knurled brake shoe elements which swing out by means ofcentrifugal force and lock against the inside diameter of the ropewinding drum commonly found on small gasoline engines. It is a furtherfeature of my invention that it may be mounted on the outside shell ofthe motor with the drive clutch mechanism fitting into, but in no wayfastened to, the inside diameter of the engine rope winding drum. It isyet a further feature of my inventionthat precision alignment of starterand motor drum is not essential since the various parts of the clutchmechanism accommodate minor alignment variations in the shaft or thedrum.. It is an additional feature of my invention that the springstarting mechanism disengages from the motor drum once the motor hasbeen started, disengagement occurring when the drum speed exceeds thatof the drive clutch element of the starter.

These and other objects and features of my invention will best beunderstood and appreciated from the following description of a preferredembodiment thereof, selected for purposes of illustration, and shown inthe accompanying drawings, in which:

Fig. 1 is a cross sectional view in side elevation showing the starterof my invention;

Fig. 2 is a cross sectional plan view along the lines 2-2 of Fig. 1; and

Fig. 3 is a view of the drive clutch mechanism taken along the lines 3-3of Fig. 1.

The preferred embodiment of my invention herein shown comprises agenerally cylindrical outer casing 10 bolted to a motor in general axialalignment with the crankshaft 12 and covering a conventional ropewinding drum 14, as it may be found on ordinary lawnmower type motors.Of course, the starter of my invention may be used lected the lawnmowertype for convenience of illustration. Where the crankshaft 12 of themotor does not employ a conventional rope winding drum 14, an element ofsimilar size and shape can be attached to the crankshaft to facilitatethe use of my invention with such a motor.

The housing 10 is provided with flanged feet 16 which facilitate boltingthe housing 10 to the motor. Internally of the housing 10 and coaxialtherewith, I mount a tube 18. In Fig. 1 the tube 18 is shown connectedto the housing 10 by a flanged element 20 which is welded to the'topinside of the housing 10. The tube 18 generally serves the purpose ofsupporting and maintaining the operating elements of the starter forrotation and in proper alignment. Thus, an inverted spring drum 22 ismounted to rotate on the tube 18, and houses a coil spring 24, one endof which is connected to the side wall of the inverted spring drum 22.The other end of the spring 24 is connected to an upstanding tubularmember 28 mounted on a relatively heavy horizontal drive disk 30. Thedrive disk 30 and its upstanding tubular member 28 fit around the tube18 in close but free sliding relationship, and they are retained inposition on the tube 18 by a retaining nut 32.

On the lower face of the drive disk 30, I mount a drive clutch mechanismwhich is adapted to fit into and clutch the inner face of the ropewinding drum 14. The drive clutch mechanism is supported by a dependingcylindrical support 34 which is bolted to the drive disk 30. Theoperating elements of the clutch are mounted on a horizontal disk 36integral with the lower end of the tubular element 34. The clutchelements themselves include a pair of pivotally mounted eccentric brakeelements 38 (see Fig. 3) pivotally connected to the disk 36 by hearingelements 40. The brake elements 38 are interconnected by a link 42 whichensures unity of motion between the two brake elements. Each brakeelement 38 is provided on its outer surface with a knurled metal orfriction brake shoe 44 mounted on the eccentric surface and in positionto engage the inner wall of the rope winding drum 14. in firm frictionalcontact when the brake elements 38 are pivoted against limit stop lugs52. In order to accommodate gross variations in drum size or shape, wearin the brake shoes 44, and unusual shaft misalignments, the brake shoes44 may be resiliently mounted on the brake elements 38-, but normally itis sufficient to make the brake elements 38 large enough to subtend anarc slightly larger than the internal arc of the rope winding drum 14.The brake elements 38 are provided with tension springs 50 for thepurpose of holding the brake elements 38 normally in the disengagedposition. The force of the spring 50, however, is selected in relationto the centrifugal and acceleration forces involved when the drive disk30 starts rotating to permit the brake elements 38 to pivot and bringthe brake shoes 44 into contact with the inner face of the rope windingdrum 14. Once the brake shoes 44 contact the rope winding drum 14,however, the brake elements 38 are turned abruptly backward by the crankshaft resistance against the stop lugs 52. In this position, the innerfaces of the brake elements 38 abut a central buttressing lug 74 whichserves to support the brake elements 38, or more specifically, the brakeshoes 44- in.

firm contact with the drum 14.

In order to wind up the spring 24 and thereby store energy in thestarter, I provide a wind-up locking mechanism for the drive disk 30.This includes a latch 54 mounted for vertical sliding motion on a keyedshaft 56 inside the housing 10. The latch 54 is positioned adjacent tothe periphery of the disk 30 and when the shaft 56 is depressed, latch54 fits between spaced teeth 55 on the rim of disk 30 preventing thedisk 30 from rotating. The upper end of the shaft 56 is provided with anoperating knob 60 by means of which the latch may be raised or loweredto lock or release the drive disk 30. The bottom riding surface of thelatch 54 is slanted at 56 to prevent its accidental entrance betweenteeth 55 when the disk 30 is rotating.

Once the drive disk 30 has been locked by the abovedescribed latchingmechanism, the spring 24 can be wound up by turning the spring drum 22.This is accomplished by means of a crank 66 mounted on the housing 10and arranged to turn a small winding gear 68 near the upper corner ofthe housing 18. This gear 68 meshes with a gear 70 mounted on the uppersurface of the spring drum 22. The spring drum 22 is restrained againstcounter rotation by means of a spring loaded pawl 72 which engages theteeth of the gear 70. 'In this way turning the crank 66 rotates thespring drum 22, and since the disk 30 is held against rotation, thespring 24 commences to store energy. When the spring 24 is fully wound,the latch 54 may be released by pulling upward on the knob 60 todisengage the latch 54 from the teeth 55 on the drive disk 30. When thishas been done, the drive disk 30 commences rotating in response to theforce of the spring 24 and, when it has reached a sufiicient rotationalvelocity, the brake elements 38 pivot outwardly in response both to theacceleration and centrifugal forces bringing the brake shoe elements 44in contact with the inner face of the rope winding drum 14. At thispoint the brake shoes 44 grab the rope winding drum 14, throwing thebrake elements 38 back against stop lugs 52 and imparting the entirekinetic energy of the drive disk 30 to the drive shaft 12. This initialshock serves to overcome the bearing friction, compression resistanceand inertia of the rotating parts of the engine, and permits me toemploy a lighter, smaller and essentially weaker spring than in previousstarters of this general type while at the same time providing anequally effective starter. Since the spring 24 is only unwound arelatively small amount by the time the brake elements grab the drum 14,the remaining energy in the spring 24 is then further imparted to thecrankshaft to turn the motor and increase the rotational velocity. Sincethe forces required for this additional turning are not as great asthose required for the initial turning, the crankshaft soon reachesoperating speeds. As the motor itself starts up, the crankshaft 12 thenstarts rotating at a faster rate than the drive disk 30, and when thishappens, the tension springs 50 pivot the brake elements 38 backwardlyand away from the inside face of the rope winding drum 14 such that therotating elements of the starter are completely disengaged from themotor and come to rest after there is no longer any turning force in thespring 24. In this condition, the starter remains at rest until themotor is stopped and again needs to be started. i 'i It will beunderstood that during the normal life a lawnmower, the starter is onlycalled upon to start the motor a relatively few number of timesestimated at from 2000 to 4000 times at the maximum. In the usualsuburban use, 500 times is probably maximum. Under these circumstancesit will be seen that carefully machined bearing surfaces areunnecessary, and considerations of metal fatigue from the kinetic energyshock during starting are minor. Thus, with the starter of my invention,the spring 24 receives a relatively abrupt shock when the brake elements38 grab the rope winding drum 14. Such would be undesirable under manyconditions of spring usage, but in the context of this invention, it iswel l within fatigue limits of conventional spring steel. On the otherhand, provision can be made to reduce this shock without departing fromthe spirit of this invention. For instance, instead of integrallyconnecting the sleeve 28 and the disk 30, the two can be connected by afriction sleeve adapted to slip under heavy impact but to hold the fullforce of the spring under more static conditions.

Similar considerations affect the construction of the brake elements 38and the brake shoes 44. Under normal conditions, no special precautionsneed be taken to withstand excessive shock or Wear. Thus, the brakeelements 38, and stop lugs 52 may be made of conventional malleableiron. In fact, the disk 36 with the stop lugs 52 and the buttressing lug74 may be conveniently cast out of malleable iron as a single piece. Thebrake shoes 44 can also be made of relatively soft metals with knurledouter faces, or they can be faced with conventional brake liningmaterials. More durable materials, however, can be employed if the needfor them arises, without departing from the spirit of the invention.

Numerous other variations of this preferred embodiment of my inventionwill now be apparent to those skilled in the art, and therefore, it isnot my intention to confine the invention to the precise form hereinshown, but rather to limit it in terms of the appended claim.

Having thus described and disclosed a preferred em bodiment of myinvention, what I claim as new and desire to secure by Letters Patent ofthe United States is:

A starter for internal combustion engines comprising an outer casing,flanges on said outer casing in such position that said outer casing canbe bolted to the internal combustion engine to be started, central tubemounted inside said outer casing, spring drum mounted on said outercasing, spring inside said spring drum with one end of said springconnected to said spring drum, drive dish mounted to rotate about saidcentral tube below said spring drum with the other end of said springattached thereto, and centrifugal force clutch mounted below said drivedisk co-axial with said central tube and in such position that when saiddrive disk achieves sufficient rotary motion, said clutch will grip theinner surface of a drum connected to the crankshaft of said internalcombustion engine and will cause said crankshaft to rotate with saiddrive disk.

References Cited in the file of this patent UNITED STATES PATENTS836,365 Coleman Nov. 20, 1906 1,864,256 Nardone June 21, 1932 1,936,554Lansing Nov. 21, 1933 1,962,962 Linder June 12, 1934 2,568,136 WeimerSept. 18, 1951 2,767,808 Nicolla Oct. 23, 1956 2,875,851 Vakos Mar. 3,1959

